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• Mysql - GROUP BY Avoid using tempoary

  - by jwzk

  The goal of this query is to get a total of unique records (by IP) per ref ID. SELECT COUNT(DISTINCT ip), GROUP_CONCAT(ref.id) FROM `sess` sess JOIN `ref` USING(row_id) WHERE sess.time BETWEEN '2010-04-21 00:00:00' AND '2010-04-21 23:59:59' GROUP BY ref.id ORDER BY sess.time DESC The query works fine, but its using a temporary table. Any ideas?

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• Identifying if a user is in the local administrators group

  - by Adam Driscoll

  My Problem I'm using PInvoked Windows API functions to verify if a user is part of the local administrators group. I'm utilizing GetCurrentProcess, OpenProcessToken, GetTokenInformationand LookupAccountSid to verify if the user is a local admin. GetTokenInformation returns a TOKEN_GROUPS struct with an array of SID_AND_ATTRIBUTES structs. I iterate over the collection and compare the user names returned by LookupAccountSid. My problem is that, locally (or more generally on our in-house domain), this works as expected. The builtin\Administrators is located within the group membership of the current process token and my method returns true. On another domain of another developer the function returns false. The LookupAccountSid functions properly for the first 2 iterations of the TOKEN_GROUPS struct, returning None and Everyone, and then craps out complaining that "A Parameter is incorrect." What would cause only two groups to work correctly? The TOKEN_GROUPS struct indicates that there are 14 groups. I'm assuming it's the SID that is invalid. Everything that I have PInvoked I have taken from an example on the PInvoke website. The only difference is that with the LookupAccountSid I have changed the Sid parameter from a byte[] to a IntPtr because SID_AND_ATTRIBUTESis also defined with an IntPtr. Is this ok since LookupAccountSid is defined with a PSID? LookupAccountSid PInvoke [DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)] static extern bool LookupAccountSid( string lpSystemName, IntPtr Sid, StringBuilder lpName, ref uint cchName, StringBuilder ReferencedDomainName, ref uint cchReferencedDomainName, out SID_NAME_USE peUse); Where the code falls over for (int i = 0; i < usize; i++) { accountCount = 0; domainCount = 0; //Get Sizes LookupAccountSid(null, tokenGroups.Groups[i].SID, null, ref accountCount, null, ref domainCount, out snu); accountName2.EnsureCapacity((int) accountCount); domainName.EnsureCapacity((int) domainCount); if (!LookupAccountSid(null, tokenGroups.Groups[i].SID, accountName2, ref accountCount, domainName, ref domainCount, out snu)) { //Finds its way here after 2 iterations //But only in a different developers domain var error = Marshal.GetLastWin32Error(); _log.InfoFormat("Failed to look up SID's account name. {0}", new Win32Exception(error).Message); continue; } If more code is needed let me know. Any help would be greatly appreciated.

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• jQuery, wont change value but will change any othere attribute...

  - by Phil Jackson

  function send_mail( token, loader ) { $(".send_mail").bind( "click", function() { try{ var to = $(this).attr('ref'); var mail_form = $("#mail_form"); mail_form.find("li:eq(0) input").val("sdsds"); //mail_form.find("li:eq(0) input").attr("ref", "sdsds"); //mail_form.find("li:eq(0) input").attr("value", "sdsds"); $.fancybox(mail_form.html(), { 'autoDimensions' : false, 'width' : 360, 'height' : 200, 'transitionIn' : 'none', 'transitionOut' : 'none', 'scrolling' : 'no', 'showCloseButton' : false }); return false; }catch(err){alert(err);} }); } My problem being that the above will not work yet if I use //mail_form.find("li:eq(0) input").attr("ref", "sdsds"); it will change the ref and even //mail_form.find("li:eq(0) input").attr("value", "sdsds"); will not work... Any ideas whats happening here?

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• To bring the IE window in front of the Screen

  - by Parameswari

  I am creating new IE browser instance dynamically, and opening a aspx page from there. Everything works fine , but the browser is not popping in the Front of the screen .Able to see the Aspx page in the task bar when I click it from there it comes to the Front . How to bring that page in front of all the Screen as soon as IE is created. I have pasted the code I used to create new IE instance. public class IEInstance { public SHDocVw.InternetExplorer IE1; public void IEInstanceCls(string check) { IE1 = new SHDocVw.InternetExplorer(); object Empty = 0; string urlpath = " "; urlpath = "http://localhost/TestPage.aspx?"; object URL = urlpath; IE1.Top = 260; IE1.Left = 900; IE1.Width = 390; IE1.Height = 460; IE1.StatusBar = false; IE1.ToolBar = 0; IE1.MenuBar = false; IE1.Visible = true; IE1.Navigate2(ref URL, ref Empty, ref Empty, ref Empty, ref Empty); } } Help me to solve this problem. Thank You

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• Reading another packages symbol table in Perl

  - by justintime

  I am trying to read a global symbol from another package. I have the package name as a string. I am using qualify_to_ref from Symbol module my $ref = qualify_to_ref ( 'myarray', 'Mypackage' ) ; my @array = @$ref ; gives me Not an ARRAY reference at ...... I presume I am getting the format of the dereference wrong. Here is a complete example program. use strict; use Symbol ; package Mypackage ; our @myarray = qw/a b/ ; package main ; my $ref = qualify_to_ref ( 'myarray', 'Mypackage' ) ; my @array = @$ref ;

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• How to create a timer the right way?

  - by mystify

  I always have an class which needs to set up a timer for as long as the object is alive. Typically an UIView which does some animation. Now the problem: If I strongly reference the NSTimer I create and invalidate and release the timer in -dealloc, the timer is never invalidated or released because -dealloc is never called, since the run loop maintains a strong reference to the target. So what can I do? If I cant hold a strong ref to the timer object, this is also bad because maybe I need a ref to it to be able to stop it. And a weak ref on a object is not good, because maybe i'm gonna access it when it's gone. So better have a retain on what I want to keep around. How are you guys solving this? must the superview create the timer? is that better? or should i really just make a weak ref on it and keep in mind that the run loop holds a strong ref on my timer for me, as long as it's not invalidated?

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• what does sizeof (function name) return?

  - by Pointer

  sample code: main () { printf ("size = %d\n", sizeof (main)); }

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• Access violation in DirectX OMSetRenderTargets

  - by IDWMaster

  I receive the following error (Unhandled exception at 0x527DAE81 (d3d11_1sdklayers.dll) in Lesson2.Triangles.exe: 0xC0000005: Access violation reading location 0x00000000) when running the Triangle sample application for DirectX 11 in D3D_FEATURE_LEVEL_9_1. This error occurs at the OMSetRenderTargets function, as shown below, and does not happen if I remove that function from the program (but then, the screen is blue, and does not render the triangle) //// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF //// ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO //// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A //// PARTICULAR PURPOSE. //// //// Copyright (c) Microsoft Corporation. All rights reserved #include #include #include "DirectXSample.h" #include "BasicMath.h" #include "BasicReaderWriter.h" using namespace Microsoft::WRL; using namespace Windows::UI::Core; using namespace Windows::Foundation; using namespace Windows::ApplicationModel::Core; using namespace Windows::ApplicationModel::Infrastructure; // This class defines the application as a whole. ref class Direct3DTutorialViewProvider : public IViewProvider { private: CoreWindow^ m_window; ComPtr m_swapChain; ComPtr m_d3dDevice; ComPtr m_d3dDeviceContext; ComPtr m_renderTargetView; public: // This method is called on application launch. void Initialize( _In_ CoreWindow^ window, _In_ CoreApplicationView^ applicationView ) { m_window = window; } // This method is called after Initialize. void Load(_In_ Platform::String^ entryPoint) { } // This method is called after Load. void Run() { // First, create the Direct3D device. // This flag is required in order to enable compatibility with Direct2D. UINT creationFlags = D3D11_CREATE_DEVICE_BGRA_SUPPORT; #if defined(_DEBUG) // If the project is in a debug build, enable debugging via SDK Layers with this flag. creationFlags |= D3D11_CREATE_DEVICE_DEBUG; #endif // This array defines the ordering of feature levels that D3D should attempt to create. D3D_FEATURE_LEVEL featureLevels[] = { D3D_FEATURE_LEVEL_11_1, D3D_FEATURE_LEVEL_11_0, D3D_FEATURE_LEVEL_10_1, D3D_FEATURE_LEVEL_10_0, D3D_FEATURE_LEVEL_9_3, D3D_FEATURE_LEVEL_9_1 }; ComPtr d3dDevice; ComPtr d3dDeviceContext; DX::ThrowIfFailed( D3D11CreateDevice( nullptr, // specify nullptr to use the default adapter D3D_DRIVER_TYPE_HARDWARE, nullptr, // leave as nullptr if hardware is used creationFlags, // optionally set debug and Direct2D compatibility flags featureLevels, ARRAYSIZE(featureLevels), D3D11_SDK_VERSION, // always set this to D3D11_SDK_VERSION &d3dDevice, nullptr, &d3dDeviceContext ) ); // Retrieve the Direct3D 11.1 interfaces. DX::ThrowIfFailed( d3dDevice.As(&m_d3dDevice) ); DX::ThrowIfFailed( d3dDeviceContext.As(&m_d3dDeviceContext) ); // After the D3D device is created, create additional application resources. CreateWindowSizeDependentResources(); // Create a Basic Reader-Writer class to load data from disk. This class is examined // in the Resource Loading sample. BasicReaderWriter^ reader = ref new BasicReaderWriter(); // Load the raw vertex shader bytecode from disk and create a vertex shader with it. auto vertexShaderBytecode = reader-ReadData("SimpleVertexShader.cso"); ComPtr vertexShader; DX::ThrowIfFailed( m_d3dDevice-CreateVertexShader( vertexShaderBytecode-Data, vertexShaderBytecode-Length, nullptr, &vertexShader ) ); // Create an input layout that matches the layout defined in the vertex shader code. // For this lesson, this is simply a float2 vector defining the vertex position. const D3D11_INPUT_ELEMENT_DESC basicVertexLayoutDesc[] = { { "POSITION", 0, DXGI_FORMAT_R32G32_FLOAT, 0, 0, D3D11_INPUT_PER_VERTEX_DATA, 0 }, }; ComPtr inputLayout; DX::ThrowIfFailed( m_d3dDevice-CreateInputLayout( basicVertexLayoutDesc, ARRAYSIZE(basicVertexLayoutDesc), vertexShaderBytecode-Data, vertexShaderBytecode-Length, &inputLayout ) ); // Load the raw pixel shader bytecode from disk and create a pixel shader with it. auto pixelShaderBytecode = reader-ReadData("SimplePixelShader.cso"); ComPtr pixelShader; DX::ThrowIfFailed( m_d3dDevice-CreatePixelShader( pixelShaderBytecode-Data, pixelShaderBytecode-Length, nullptr, &pixelShader ) ); // Create vertex and index buffers that define a simple triangle. float3 triangleVertices[] = { float3(-0.5f, -0.5f,13.5f), float3( 0.0f, 0.5f,0), float3( 0.5f, -0.5f,0), }; D3D11_BUFFER_DESC vertexBufferDesc = {0}; vertexBufferDesc.ByteWidth = sizeof(float3) * ARRAYSIZE(triangleVertices); vertexBufferDesc.Usage = D3D11_USAGE_DEFAULT; vertexBufferDesc.BindFlags = D3D11_BIND_VERTEX_BUFFER; vertexBufferDesc.CPUAccessFlags = 0; vertexBufferDesc.MiscFlags = 0; vertexBufferDesc.StructureByteStride = 0; D3D11_SUBRESOURCE_DATA vertexBufferData; vertexBufferData.pSysMem = triangleVertices; vertexBufferData.SysMemPitch = 0; vertexBufferData.SysMemSlicePitch = 0; ComPtr vertexBuffer; DX::ThrowIfFailed( m_d3dDevice-CreateBuffer( &vertexBufferDesc, &vertexBufferData, &vertexBuffer ) ); // Once all D3D resources are created, configure the application window. // Allow the application to respond when the window size changes. m_window-SizeChanged += ref new TypedEventHandler( this, &Direct3DTutorialViewProvider::OnWindowSizeChanged ); // Specify the cursor type as the standard arrow cursor. m_window-PointerCursor = ref new CoreCursor(CoreCursorType::Arrow, 0); // Activate the application window, making it visible and enabling it to receive events. m_window-Activate(); // Enter the render loop. Note that tailored applications should never exit. while (true) { // Process events incoming to the window. m_window-Dispatcher-ProcessEvents(CoreProcessEventsOption::ProcessAllIfPresent); // Specify the render target we created as the output target. ID3D11RenderTargetView* targets[1] = {m_renderTargetView.Get()}; m_d3dDeviceContext-OMSetRenderTargets( 1, targets, NULL // use no depth stencil ); // Clear the render target to a solid color. const float clearColor[4] = { 0.071f, 0.04f, 0.561f, 1.0f }; //Code fails here m_d3dDeviceContext-ClearRenderTargetView( m_renderTargetView.Get(), clearColor ); m_d3dDeviceContext-IASetInputLayout(inputLayout.Get()); // Set the vertex and index buffers, and specify the way they define geometry. UINT stride = sizeof(float3); UINT offset = 0; m_d3dDeviceContext-IASetVertexBuffers( 0, 1, vertexBuffer.GetAddressOf(), &stride, &offset ); m_d3dDeviceContext-IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_TRIANGLELIST); // Set the vertex and pixel shader stage state. m_d3dDeviceContext-VSSetShader( vertexShader.Get(), nullptr, 0 ); m_d3dDeviceContext-PSSetShader( pixelShader.Get(), nullptr, 0 ); // Draw the cube. m_d3dDeviceContext-Draw(3,0); // Present the rendered image to the window. Because the maximum frame latency is set to 1, // the render loop will generally be throttled to the screen refresh rate, typically around // 60Hz, by sleeping the application on Present until the screen is refreshed. DX::ThrowIfFailed( m_swapChain-Present(1, 0) ); } } // This method is called before the application exits. void Uninitialize() { } private: // This method is called whenever the application window size changes. void OnWindowSizeChanged( _In_ CoreWindow^ sender, _In_ WindowSizeChangedEventArgs^ args ) { m_renderTargetView = nullptr; CreateWindowSizeDependentResources(); } // This method creates all application resources that depend on // the application window size. It is called at app initialization, // and whenever the application window size changes. void CreateWindowSizeDependentResources() { if (m_swapChain != nullptr) { // If the swap chain already exists, resize it. DX::ThrowIfFailed( m_swapChain-ResizeBuffers( 2, 0, 0, DXGI_FORMAT_R8G8B8A8_UNORM, 0 ) ); } else { // If the swap chain does not exist, create it. DXGI_SWAP_CHAIN_DESC1 swapChainDesc = {0}; swapChainDesc.Stereo = false; swapChainDesc.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT; swapChainDesc.Scaling = DXGI_SCALING_NONE; swapChainDesc.Flags = 0; // Use automatic sizing. swapChainDesc.Width = 0; swapChainDesc.Height = 0; // This is the most common swap chain format. swapChainDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM; // Don't use multi-sampling. swapChainDesc.SampleDesc.Count = 1; swapChainDesc.SampleDesc.Quality = 0; // Use two buffers to enable flip effect. swapChainDesc.BufferCount = 2; // We recommend using this swap effect for all applications. swapChainDesc.SwapEffect = DXGI_SWAP_EFFECT_FLIP_SEQUENTIAL; // Once the swap chain description is configured, it must be // created on the same adapter as the existing D3D Device. // First, retrieve the underlying DXGI Device from the D3D Device. ComPtr dxgiDevice; DX::ThrowIfFailed( m_d3dDevice.As(&dxgiDevice) ); // Ensure that DXGI does not queue more than one frame at a time. This both reduces // latency and ensures that the application will only render after each VSync, minimizing // power consumption. DX::ThrowIfFailed( dxgiDevice-SetMaximumFrameLatency(1) ); // Next, get the parent factory from the DXGI Device. ComPtr dxgiAdapter; DX::ThrowIfFailed( dxgiDevice-GetAdapter(&dxgiAdapter) ); ComPtr dxgiFactory; DX::ThrowIfFailed( dxgiAdapter-GetParent( __uuidof(IDXGIFactory2), &dxgiFactory ) ); // Finally, create the swap chain. DX::ThrowIfFailed( dxgiFactory-CreateSwapChainForImmersiveWindow( m_d3dDevice.Get(), DX::GetIUnknown(m_window), &swapChainDesc, nullptr, // allow on all displays &m_swapChain ) ); } // Once the swap chain is created, create a render target view. This will // allow Direct3D to render graphics to the window. ComPtr backBuffer; DX::ThrowIfFailed( m_swapChain-GetBuffer( 0, __uuidof(ID3D11Texture2D), &backBuffer ) ); DX::ThrowIfFailed( m_d3dDevice-CreateRenderTargetView( backBuffer.Get(), nullptr, &m_renderTargetView ) ); // After the render target view is created, specify that the viewport, // which describes what portion of the window to draw to, should cover // the entire window. D3D11_TEXTURE2D_DESC backBufferDesc = {0}; backBuffer-GetDesc(&backBufferDesc); D3D11_VIEWPORT viewport; viewport.TopLeftX = 0.0f; viewport.TopLeftY = 0.0f; viewport.Width = static_cast(backBufferDesc.Width); viewport.Height = static_cast(backBufferDesc.Height); viewport.MinDepth = D3D11_MIN_DEPTH; viewport.MaxDepth = D3D11_MAX_DEPTH; m_d3dDeviceContext-RSSetViewports(1, &viewport); } }; // This class defines how to create the custom View Provider defined above. ref class Direct3DTutorialViewProviderFactory : IViewProviderFactory { public: IViewProvider^ CreateViewProvider() { return ref new Direct3DTutorialViewProvider(); } }; [Platform::MTAThread] int main(array^) { auto viewProviderFactory = ref new Direct3DTutorialViewProviderFactory(); Windows::ApplicationModel::Core::CoreApplication::Run(viewProviderFactory); return 0; }

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• Marshalling the value of a char* ANSI string DLL API parameter into a C# string

  - by Brian Biales

  For those who do not mix .NET C# code with legacy DLL's that use char* pointers on a regular basis, the process to convert the strings one way or the other is non-obvious. This is not a comprehensive article on the topic at all, but rather an example of something that took me some time to go find, maybe it will save someone else the time. I am utilizing a third party too that uses a call back function to inform my application of its progress.  This callback includes a pointer that under some circumstances is a pointer to an ANSI character string.  I just need to marshal it into a C# string variable.  Seems pretty simple, yes?  Well, it is, (as are most things, once you know how to do them). The parameter of my callback function is of type IntPtr, which implies it is an integer representation of a pointer.  If I know the pointer is pointing to a simple ANSI string, here is a simple static method to copy it to a C# string: private static string GetStringFromCharStar(IntPtr ptr) {     return System.Runtime.InteropServices.Marshal.PtrToStringAnsi(ptr); } The System.Runtime.InteropServices is where to look any time you are mixing legacy unmanaged code with your .NET application.

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• Shared pointers causing weird behaviour

  - by Setzer22

  I have the following code in SFML 2.1 Class ResourceManager: shared_ptr<Sprite> ResourceManager::getSprite(string name) { shared_ptr<Texture> texture(new Texture); if(!texture->loadFromFile(resPath+spritesPath+name)) throw new NotSuchFileException(); shared_ptr<Sprite> sprite(new Sprite(*texture)); return sprite; } Main method: (I'll omit most of the irrelevant code shared_ptr<Sprite> sprite = ResourceManager::getSprite("sprite.png"); ... while(renderWindow.isOpen()) renderWindow.draw(*sprite); Oddly enough this makes my sprite render completely white, but if I do this instead: shared_ptr<Sprite> ResourceManager::getSprite(string name) { Texture* texture = new Texture; // <------- From shared pointer to pointer if(!texture->loadFromFile(resPath+spritesPath+name)) throw new NotSuchFileException(); shared_ptr<Sprite> sprite(new Sprite(*texture)); return sprite; } It works perfectly. So what's happening here? I assumed the shared pointer would work just as a pointer. Could it be that it's getting deleted? My main method is keeping a reference to it so I don't really understand what's going on here :S EDIT: I'm perfectly aware deleting the sprite won't delete the texture and this is generating a memory leak I'd have to handle, that's why I'm trying to use smart pointers on the first place...

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• Efficiency of iterators and alternatives? [migrated]

  - by user48037

  I have the following code for my game tiles: std::vector<GameObject_Tile*>::iterator it; for(int y = 0; y < GAME_TILES_Y; y++) { for(int x = 0; x < GAME_TILES_X; x++) { for (it = gameTiles[x][y].tiles.begin() ; it != gameTiles[x][y].tiles.end(); ++it) {}}} tiles is: struct Game_Tile { // More specific object types will be added here eventually vector<GameObject_Tile*> tiles; }; My problem is that if I change the vector to just be a single GameObject_Tile* instead and remove the iterator line in the loop I go from about 200fps to 450fps. Some context: The vector/pointer only contains one object in both scenarios. I will eventually need to store multiple, but for testing I just set it to a single pointer. The loop goes through 2,300 objects each frame and draws them. I would like to point out that if I remove the Draw (not seen int he example) method, I gain about 30 frames in both scenarios, the issue is the iteration. So I am wondering why having this as a vector being looped through by an iterator (to get at a single object) is costing me over 200 frames when compared to it being a single pointer? The 200+ frames faster code is: std::vector<GameObject_Tile*>::iterator it; for(int y = 0; y < GAME_TILES_Y; y++) { for(int x = 0; x < GAME_TILES_X; x++) { //gameTiles[x][y].tiles is used as a pointer here instead of using *it }} tiles is: struct Game_Tile { // More specific object types will be added here eventually GameObject_Tile* tiles; };

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• how to clear stack after stack overflow signal occur

  - by user353573

  In pthread, After reaching yellow zone in stack, signal handler stop the recursive function by making it return however, we can only continue to use extra area in yellow zone, how to clear the rubbish before the yellow zone in the thread stack ? (Copied from "answers"): #include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <signal.h> #include <setjmp.h> #include <sys/mman.h> #include <unistd.h> #include <assert.h> #include <sys/resource.h> #define ALT_STACK_SIZE (64*1024) #define YELLOW_ZONE_PAGES (1) typedef struct { size_t stack_size; char* stack_pointer; char* red_zone_boundary; char* yellow_zone_boundary; sigjmp_buf return_point; size_t red_zone_size; } ThreadInfo; static pthread_key_t thread_info_key; static struct sigaction newAct, oldAct; bool gofromyellow = false; int call_times = 0; static void main_routine(){ // make it overflow if(gofromyellow == true) { printf("return from yellow zone, called %d times\n", call_times); return; } else { call_times = call_times + 1; main_routine(); gofromyellow = true; } } // red zone management static void stackoverflow_routine(){ fprintf(stderr, "stack overflow error.\n"); fflush(stderr); } // yellow zone management static void yellow_zone_hook(){ fprintf(stderr, "exceed yellow zone.\n"); fflush(stderr); } static int get_stack_info(void** stackaddr, size_t* stacksize){ int ret = -1; pthread_attr_t attr; pthread_attr_init(&attr); if(pthread_getattr_np(pthread_self(), &attr) == 0){ ret = pthread_attr_getstack(&attr, stackaddr, stacksize); } pthread_attr_destroy(&attr); return ret; } static int is_in_stack(const ThreadInfo* tinfo, char* pointer){ return (tinfo->stack_pointer <= pointer) && (pointer < tinfo->stack_pointer + tinfo->stack_size); } static int is_in_red_zone(const ThreadInfo* tinfo, char* pointer){ if(tinfo->red_zone_boundary){ return (tinfo->stack_pointer <= pointer) && (pointer < tinfo->red_zone_boundary); } } static int is_in_yellow_zone(const ThreadInfo* tinfo, char* pointer){ if(tinfo->yellow_zone_boundary){ return (tinfo->red_zone_boundary <= pointer) && (pointer < tinfo->yellow_zone_boundary); } } static void set_yellow_zone(ThreadInfo* tinfo){ int pagesize = sysconf(_SC_PAGE_SIZE); assert(pagesize > 0); tinfo->yellow_zone_boundary = tinfo->red_zone_boundary + pagesize * YELLOW_ZONE_PAGES; mprotect(tinfo->red_zone_boundary, pagesize * YELLOW_ZONE_PAGES, PROT_NONE); } static void reset_yellow_zone(ThreadInfo* tinfo){ size_t pagesize = tinfo->yellow_zone_boundary - tinfo->red_zone_boundary; if(mmap(tinfo->red_zone_boundary, pagesize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0) == 0){ perror("mmap failed"), exit(1); } mprotect(tinfo->red_zone_boundary, pagesize, PROT_READ | PROT_WRITE); tinfo->yellow_zone_boundary = 0; } static void signal_handler(int sig, siginfo_t* sig_info, void* sig_data){ if(sig == SIGSEGV){ ThreadInfo* tinfo = (ThreadInfo*) pthread_getspecific(thread_info_key); char* fault_address = (char*) sig_info->si_addr; if(is_in_stack(tinfo, fault_address)){ if(is_in_red_zone(tinfo, fault_address)){ siglongjmp(tinfo->return_point, 1); }else if(is_in_yellow_zone(tinfo, fault_address)){ reset_yellow_zone(tinfo); yellow_zone_hook(); gofromyellow = true; return; } else { //inside stack not related overflow SEGV happen } } } } static void register_application_info(){ pthread_key_create(&thread_info_key, NULL); sigemptyset(&newAct.sa_mask); sigaddset(&newAct.sa_mask, SIGSEGV); newAct.sa_sigaction = signal_handler; newAct.sa_flags = SA_SIGINFO | SA_RESTART | SA_ONSTACK; sigaction(SIGSEGV, &newAct, &oldAct); } static void register_thread_info(ThreadInfo* tinfo){ stack_t ss; pthread_setspecific(thread_info_key, tinfo); get_stack_info((void**)&tinfo->stack_pointer, &tinfo->stack_size); printf("stack size %d mb\n", tinfo->stack_size/1024/1024 ); tinfo->red_zone_boundary = tinfo->stack_pointer + tinfo->red_zone_size; set_yellow_zone(tinfo); ss.ss_sp = (char*)malloc(ALT_STACK_SIZE); ss.ss_size = ALT_STACK_SIZE; ss.ss_flags = 0; sigaltstack(&ss, NULL); } static void* thread_routine(void* p){ ThreadInfo* tinfo = (ThreadInfo*)p; register_thread_info(tinfo); if(sigsetjmp(tinfo->return_point, 1) == 0){ main_routine(); } else { stackoverflow_routine(); } free(tinfo); printf("after tinfo, end thread\n"); return 0; } int main(int argc, char** argv){ register_application_info(); if( argc == 2 ){ int stacksize = atoi(argv[1]); pthread_attr_t attr; pthread_attr_init(&attr); pthread_attr_setstacksize(&attr, 1024 * 1024 * stacksize); { pthread_t pid0; ThreadInfo* tinfo = (ThreadInfo*)calloc(1, sizeof(ThreadInfo)); pthread_attr_getguardsize(&attr, &tinfo->red_zone_size); pthread_create(&pid0, &attr, thread_routine, tinfo); pthread_join(pid0, NULL); } } else { printf("Usage: %s stacksize(mb)\n", argv[0]); } return 0; } C language in linux, ubuntu

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• How should I change my Graph structure (very slow insertion)?

  - by Nazgulled

  Hi, This program I'm doing is about a social network, which means there are users and their profiles. The profiles structure is UserProfile. Now, there are various possible Graph implementations and I don't think I'm using the best one. I have a Graph structure and inside, there's a pointer to a linked list of type Vertex. Each Vertex element has a value, a pointer to the next Vertex and a pointer to a linked list of type Edge. Each Edge element has a value (so I can define weights and whatever it's needed), a pointer to the next Edge and a pointer to the Vertex owner. I have a 2 sample files with data to process (in CSV style) and insert into the Graph. The first one is the user data (one user per line); the second one is the user relations (for the graph). The first file is quickly inserted into the graph cause I always insert at the head and there's like ~18000 users. The second file takes ages but I still insert the edges at the head. The file has about ~520000 lines of user relations and takes between 13-15mins to insert into the Graph. I made a quick test and reading the data is pretty quickly, instantaneously really. The problem is in the insertion. This problem exists because I have a Graph implemented with linked lists for the vertices. Every time I need to insert a relation, I need to lookup for 2 vertices, so I can link them together. This is the problem... Doing this for ~520000 relations, takes a while. How should I solve this? Solution 1) Some people recommended me to implement the Graph (the vertices part) as an array instead of a linked list. This way I have direct access to every vertex and the insertion is probably going to drop considerably. But, I don't like the idea of allocating an array with [18000] elements. How practically is this? My sample data has ~18000, but what if I need much less or much more? The linked list approach has that flexibility, I can have whatever size I want as long as there's memory for it. But the array doesn't, how am I going to handle such situation? What are your suggestions? Using linked lists is good for space complexity but bad for time complexity. And using an array is good for time complexity but bad for space complexity. Any thoughts about this solution? Solution 2) This project also demands that I have some sort of data structures that allows quick lookup based on a name index and an ID index. For this I decided to use Hash Tables. My tables are implemented with separate chaining as collision resolution and when a load factor of 0.70 is reach, I normally recreate the table. I base the next table size on this http://planetmath.org/encyclopedia/GoodHashTablePrimes.html. Currently, both Hash Tables hold a pointer to the UserProfile instead of duplication the user profile itself. That would be stupid, changing data would require 3 changes and it's really dumb to do it that way. So I just save the pointer to the UserProfile. The same user profile pointer is also saved as value in each Graph Vertex. So, I have 3 data structures, one Graph and two Hash Tables and every single one of them point to the same exact UserProfile. The Graph structure will serve the purpose of finding the shortest path and stuff like that while the Hash Tables serve as quick index by name and ID. What I'm thinking to solve my Graph problem is to, instead of having the Hash Tables value point to the UserProfile, I point it to the corresponding Vertex. It's still a pointer, no more and no less space is used, I just change what I point to. Like this, I can easily and quickly lookup for each Vertex I need and link them together. This will insert the ~520000 relations pretty quickly. I thought of this solution because I already have the Hash Tables and I need to have them, then, why not take advantage of them for indexing the Graph vertices instead of the user profile? It's basically the same thing, I can still access the UserProfile pretty quickly, just go to the Vertex and then to the UserProfile. But, do you see any cons on this second solution against the first one? Or only pros that overpower the pros and cons on the first solution? Other Solution) If you have any other solution, I'm all ears. But please explain the pros and cons of that solution over the previous 2. I really don't have much time to be wasting with this right now, I need to move on with this project, so, if I'm doing to do such a change, I need to understand exactly what to change and if that's really the way to go. Hopefully no one fell asleep reading this and closed the browser, sorry for the big testament. But I really need to decide what to do about this and I really need to make a change. P.S: When answering my proposed solutions, please enumerate them as I did so I know exactly what are you talking about and don't confuse my self more than I already am.

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• OpenGL loading functions error [on hold]

  - by Ghilliedrone

  I'm new to OpenGL, and I bought a book on it for beginners. I finished writing the sample code for making a context/window. I get an error on this line at the part PFNWGLCREATECONTEXTATTRIBSARBPROC, saying "Error: expected a ')'": typedef HGLRC(APIENTRYP PFNWGLCREATECONTEXTATTRIBSARBPROC)(HDC, HGLRC, const int*); Replacing it or adding a ")" makes it error, but the error disappears when I use the OpenGL headers included in the books CD, which are OpenGL 3.0. I would like a way to make this work with the newest gl.h/wglext.h and without libraries. Here's the rest of the class if it's needed: #include <ctime> #include <windows.h> #include <iostream> #include <gl\GL.h> #include <gl\wglext.h> #include "Example.h" #include "GLWindow.h" typedef HGLRC(APIENTRYP PFNWGLCREATECONTEXTATTRIBSARBPROC)(HDC, HGLRC, const int*); PFNWGLCREATECONTEXTATTRIBSARBPROC wglCreateContextAttribsARB = NULL; bool GLWindow::create(int width, int height, int bpp, bool fullscreen) { DWORD dwExStyle; //Window Extended Style DWORD dwStyle; //Window Style m_isFullscreen = fullscreen;//Store the fullscreen flag m_windowRect.left = 0L; m_windowRect.right = (long)width; m_windowRect.top = 0L; m_windowRect.bottom = (long)height;//Set bottom to height // fill out the window class structure m_windowClass.cbSize = sizeof(WNDCLASSEX); m_windowClass.style = CS_HREDRAW | CS_VREDRAW; m_windowClass.lpfnWndProc = GLWindow::StaticWndProc; //We set our static method as the event handler m_windowClass.cbClsExtra = 0; m_windowClass.cbWndExtra = 0; m_windowClass.hInstance = m_hinstance; m_windowClass.hIcon = LoadIcon(NULL, IDI_APPLICATION); // default icon m_windowClass.hCursor = LoadCursor(NULL, IDC_ARROW); // default arrow m_windowClass.hbrBackground = NULL; // don't need background m_windowClass.lpszMenuName = NULL; // no menu m_windowClass.lpszClassName = (LPCWSTR)"GLClass"; m_windowClass.hIconSm = LoadIcon(NULL, IDI_WINLOGO); // windows logo small icon if (!RegisterClassEx(&m_windowClass)) { MessageBox(NULL, (LPCWSTR)"Failed to register window class", NULL, MB_OK); return false; } if (m_isFullscreen)//If we are fullscreen, we need to change the display { DEVMODE dmScreenSettings; //Device mode memset(&dmScreenSettings, 0, sizeof(dmScreenSettings)); dmScreenSettings.dmSize = sizeof(dmScreenSettings); dmScreenSettings.dmPelsWidth = width; //Screen width dmScreenSettings.dmPelsHeight = height; //Screen height dmScreenSettings.dmBitsPerPel = bpp; //Bits per pixel dmScreenSettings.dmFields = DM_BITSPERPEL | DM_PELSWIDTH | DM_PELSHEIGHT; if (ChangeDisplaySettings(&dmScreenSettings, CDS_FULLSCREEN) != DISP_CHANGE_SUCCESSFUL) { MessageBox(NULL, (LPCWSTR)"Display mode failed", NULL, MB_OK); m_isFullscreen = false; } } if (m_isFullscreen) //Is it fullscreen? { dwExStyle = WS_EX_APPWINDOW; //Window Extended Style dwStyle = WS_POPUP; //Windows Style ShowCursor(false); //Hide mouse pointer } else { dwExStyle = WS_EX_APPWINDOW | WS_EX_WINDOWEDGE; //Window Exteneded Style dwStyle = WS_OVERLAPPEDWINDOW; //Windows Style } AdjustWindowRectEx(&m_windowRect, dwStyle, false, dwExStyle); //Adjust window to true requested size //Class registered, so now create window m_hwnd = CreateWindowEx(NULL, //Extended Style (LPCWSTR)"GLClass", //Class name (LPCWSTR)"Chapter 2", //App name dwStyle | WS_CLIPCHILDREN | WS_CLIPSIBLINGS, 0, 0, //x, y coordinates m_windowRect.right - m_windowRect.left, m_windowRect.bottom - m_windowRect.top, //Width and height NULL, //Handle to parent NULL, //Handle to menu m_hinstance, //Application instance this); //Pass a pointer to the GLWindow here //Check if window creation failed, hwnd would equal NULL if (!m_hwnd) { return 0; } m_hdc = GetDC(m_hwnd); ShowWindow(m_hwnd, SW_SHOW); UpdateWindow(m_hwnd); m_lastTime = GetTickCount() / 1000.0f; return true; } LRESULT CALLBACK GLWindow::StaticWndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam) { GLWindow* window = nullptr; //If this is the create message if (uMsg == WM_CREATE) { //Get the pointer we stored during create window = (GLWindow*)((LPCREATESTRUCT)lParam)->lpCreateParams; //Associate the window pointer with the hwnd for the other events to access SetWindowLongPtr(hWnd, GWL_USERDATA, (LONG_PTR)window); } else { //If this is not a creation event, then we should have stored a pointer to the window window = (GLWindow*)GetWindowLongPtr(hWnd, GWL_USERDATA); if (!window) { //Do the default event handling return DefWindowProc(hWnd, uMsg, wParam, lParam); } } //Call our window's member WndProc(allows us to access member variables) return window->WndProc(hWnd, uMsg, wParam, lParam); } LRESULT GLWindow::WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam) { switch (uMsg) { case WM_CREATE: { m_hdc = GetDC(hWnd); setupPixelFormat(); //Set the version that we want, in this case 3.0 int attribs[] = { WGL_CONTEXT_MAJOR_VERSION_ARB, 3, WGL_CONTEXT_MINOR_VERSION_ARB, 0, 0}; //Create temporary context so we can get a pointer to the function HGLRC tmpContext = wglCreateContext(m_hdc); //Make the context current wglMakeCurrent(m_hdc, tmpContext); //Get the function pointer wglCreateContextAttribsARB = (PFNWGLCREATECONTEXTATTRIBSARBPROC)wglGetProcAddress("wglCreateContextAttribsARB"); //If this is NULL then OpenGl 3.0 is not supported if (!wglCreateContextAttribsARB) { MessageBox(NULL, (LPCWSTR)"OpenGL 3.0 is not supported", (LPCWSTR)"An error occured", MB_ICONERROR | MB_OK); DestroyWindow(hWnd); return 0; } //Create an OpenGL 3.0 context using the new function m_hglrc = wglCreateContextAttribsARB(m_hdc, 0, attribs); //Delete the temporary context wglDeleteContext(tmpContext); //Make the GL3 context current wglMakeCurrent(m_hdc, m_hglrc); m_isRunning = true; } break; case WM_DESTROY: //Window destroy case WM_CLOSE: //Windows is closing wglMakeCurrent(m_hdc, NULL); wglDeleteContext(m_hglrc); m_isRunning = false; //Stop the main loop PostQuitMessage(0); break; case WM_SIZE: { int height = HIWORD(lParam); //Get height and width int width = LOWORD(lParam); getAttachedExample()->onResize(width, height); //Call the example's resize method } break; case WM_KEYDOWN: if (wParam == VK_ESCAPE) //If the escape key was pressed { DestroyWindow(m_hwnd); } break; default: break; } return DefWindowProc(hWnd, uMsg, wParam, lParam); } void GLWindow::processEvents() { MSG msg; //While there are messages in the queue, store them in msg while (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) { //Process the messages TranslateMessage(&msg); DispatchMessage(&msg); } } Here is the header: #pragma once #include <ctime> #include <windows.h> class Example;//Declare our example class class GLWindow { public: GLWindow(HINSTANCE hInstance); //default constructor bool create(int width, int height, int bpp, bool fullscreen); void destroy(); void processEvents(); void attachExample(Example* example); bool isRunning(); //Is the window running? void swapBuffers() { SwapBuffers(m_hdc); } static LRESULT CALLBACK StaticWndProc(HWND wnd, UINT msg, WPARAM wParam, LPARAM lParam); LRESULT CALLBACK WndProc(HWND wnd, UINT msg, WPARAM wParam, LPARAM lParam); float getElapsedSeconds(); private: Example* m_example; //A link to the example program bool m_isRunning; //Is the window still running? bool m_isFullscreen; HWND m_hwnd; //Window handle HGLRC m_hglrc; //Rendering context HDC m_hdc; //Device context RECT m_windowRect; //Window bounds HINSTANCE m_hinstance; //Application instance WNDCLASSEX m_windowClass; void setupPixelFormat(void); Example* getAttachedExample() { return m_example; } float m_lastTime; };

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• tunnel effect cocos2d

  - by samfisher

  I am looking to create a similar tunnel effect in COCOS2D (iOS). Could anyone suggest any pointers? ref Video 1 ref Video 2 Till now I have tried with several ring shape sprites with decreasing scale and positioned center to a same point and keeping Z decreasing as well for each smaller sprite. With that, animating it with CCScaleTo and changing the size to 2.0 with animation duration but it does not come anyway near to the tunnel effect shown in the reference. Thanks, sam

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• JNDI Datasource definition in Tomcat 6.0

  - by romaintaz

  I want to define a DataSource to an Oracle database on my Tomcat 6.0. So, in conf/server.xml (yes, I know that this DataSource will be available for all the webapps in Tomcat, but it's not a problem here), I've set this Resource: <GlobalNamingResources> <Resource name="hibernate/HibernateDS" auth="Container" type="javax.sql.DataSource" url="jdbc:oracle:thin:@myserver:1542:foo" username="foo" password="bar" driverClassName="oracle.jdbc.OracleDriver" maxActive="50" maxIdle="10" validationQuery="select 1 from dual"/> Then, in the web.xml of my application, I set a resource-ref element: <resource-ref> <description>Hibernate Datasource</description> <res-ref-name>hibernate/HibernateDS</res-ref-name> <res-type>javax.sql.DataSource</res-type> <res-auth>Container</res-auth> </resource-ref> Finally, as Hibernate is used to manage the database connection, I have a webapps/mywebapp/WEB-INF/classes/hibernate.cfg.xml that creates a session-factory using the JNDI DataSource: <hibernate-configuration> <session-factory> <property name="connection.datasource">java:comp/env/hibernate/HibernateDS</property> ... However, when I start my Tomcat server, I get an error that says it could not create the INFO [net.sf.hibernate.util.NamingHelper] JNDI InitialContext properties:{} INFO [net.sf.hibernate.connection.DatasourceConnectionProvider] Using datasource: java:comp/env/hibernate/HibernateDS INFO [net.sf.hibernate.transaction.TransactionFactoryFactory] Transaction strategy: net.sf.hibernate.transaction.JDBCTransactionFactory INFO [net.sf.hibernate.transaction.TransactionManagerLookupFactory] No TransactionManagerLookup configured (in JTA environment, use of process level read-write cache is not recommended) WARN [net.sf.hibernate.cfg.SettingsFactory] Could not obtain connection metadata org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot create JDBC driver of class '' for connect URL 'null' at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1150) at org.apache.tomcat.dbcp.dbcp.BasicDataSource.getConnection(BasicDataSource.java:880) at net.sf.hibernate.connection.DatasourceConnectionProvider.getConnection(DatasourceConnectionProvider.java:59) at net.sf.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:84) at net.sf.hibernate.cfg.Configuration.buildSettings(Configuration.java:1172) ... Caused by: java.lang.NullPointerException at sun.jdbc.odbc.JdbcOdbcDriver.getProtocol(JdbcOdbcDriver.java:507) at sun.jdbc.odbc.JdbcOdbcDriver.knownURL(JdbcOdbcDriver.java:476) at sun.jdbc.odbc.JdbcOdbcDriver.acceptsURL(JdbcOdbcDriver.java:307) at java.sql.DriverManager.getDriver(DriverManager.java:253) at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1143) ... 11 more Do you have any idea why Hibernate is not able to construct the session-factory? What is wrong in my configuration?

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• JNDI Datasource definition in Tomcat 6.0

  - by romaintaz

  Hi all, I want to define a DataSource to an Oracle database on my Tomcat 6.0. So, in conf/server.xml (yes, I know that this DataSource will be available for all the webapps in Tomcat, but it's not a problem here), I've set this Resource: <GlobalNamingResources> <Resource name="hibernate/HibernateDS" auth="Container" type="javax.sql.DataSource" url="jdbc:oracle:thin:@myserver:1542:foo" username="foo" password="bar" driverClassName="oracle.jdbc.OracleDriver" maxActive="50" maxIdle="10" validationQuery="select 1 from dual"/> Then, in the web.xml of my application, I set a resource-ref element: <resource-ref> <description>Hibernate Datasource</description> <res-ref-name>hibernate/HibernateDS</res-ref-name> <res-type>javax.sql.DataSource</res-type> <res-auth>Container</res-auth> </resource-ref> Finally, as Hibernate is used to manage the database connection, I have a webapps/mywebapp/WEB-INF/classes/hibernate.cfg.xml that creates a session-factory using the JNDI DataSource: <hibernate-configuration> <session-factory> <property name="connection.datasource">java:comp/env/hibernate/HibernateDS</property> ... However, when I start my Tomcat server, I get an error that says it could not create the INFO [net.sf.hibernate.util.NamingHelper] JNDI InitialContext properties:{} INFO [net.sf.hibernate.connection.DatasourceConnectionProvider] Using datasource: java:comp/env/hibernate/HibernateDS INFO [net.sf.hibernate.transaction.TransactionFactoryFactory] Transaction strategy: net.sf.hibernate.transaction.JDBCTransactionFactory INFO [net.sf.hibernate.transaction.TransactionManagerLookupFactory] No TransactionManagerLookup configured (in JTA environment, use of process level read-write cache is not recommended) WARN [net.sf.hibernate.cfg.SettingsFactory] Could not obtain connection metadata org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot create JDBC driver of class '' for connect URL 'null' at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1150) at org.apache.tomcat.dbcp.dbcp.BasicDataSource.getConnection(BasicDataSource.java:880) at net.sf.hibernate.connection.DatasourceConnectionProvider.getConnection(DatasourceConnectionProvider.java:59) at net.sf.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:84) at net.sf.hibernate.cfg.Configuration.buildSettings(Configuration.java:1172) ... Caused by: java.lang.NullPointerException at sun.jdbc.odbc.JdbcOdbcDriver.getProtocol(JdbcOdbcDriver.java:507) at sun.jdbc.odbc.JdbcOdbcDriver.knownURL(JdbcOdbcDriver.java:476) at sun.jdbc.odbc.JdbcOdbcDriver.acceptsURL(JdbcOdbcDriver.java:307) at java.sql.DriverManager.getDriver(DriverManager.java:253) at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1143) ... 11 more Do you have any idea why Hibernate is not able to construct the session-factory? What is wrong in my configuration?

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• Mouse not working after upgrade

  - by Gaz

  After upgrade from 12.4 to 13.4 my usb mouse does not respond. Unlike similar posts my keyboard works (Alt + Tab, num loc etc) which means I can enter password and still log into desktop but still with no mouse support. I have tried other usb and PS2 mice (Logitech and Microsoft mouse) that are working on other Systems with no success. When running "xsetpointer -1 | grep Pointer" in terminal window as per post USB Mouse not recognized it shows no mouse installed. When the mouse is plugged in the light under mouse illuminates so their is power to mouse. In KDE by using the keyboard I was able to turn on "Move pointer with keyboard (using num pad)" from the "Mouse - KDE Control Module" which allowed me to move the mouse pointer using the keyboard. Without complete reinstall how do I get mouse working again?

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• C++ Pointers: Number of levels of Indirection

  - by A B

  In a C++ program that doesn't contain legacy C code, is there a guideline regarding the maximum number of levels of indirection that should be used in the source code? I know that in C (as opposed to C++), some programmers have used pointers to pointers for a multiple dimension array, but for the case of arrays, there are data structures in C++ that can be used to avoid the pointers to pointers. Are users who still create pointers to pointers (or more than this) trying to use pointers to pointers only for performance ETC. reasons? I have tried NOT to use any more than a pointer to a pointer, only in the case that a pointer needed modification; does anyone have any other official or unofficial guidelines or rules regarding the number of levels of indirection?

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• Am I allowed to display a small image on top of a Google Maps Static Api map?

  - by Fábio Santos

  I am the webmaster to my company's website. I was asked to make the Google Map on this page smaller, but the interactive map doesn't work well at all at 300x200. I was asked to place a screenshot there but since that seems to be a violation of Google's terms I decided to use the Static Maps API. As you can see, on the page, I have a custom pointer icon. I don't want to lose it, so I intend to use HTML and CSS to place the pointer over the map, thus replacing the original pointer on the client side. Am I allowed to do that?

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• About insertion sort and especially why it's said that copy is much faster than swap?

  - by Software Engeneering Learner

  From Lafore's "Data Structures and Algorithms in Java": (about insertion sort (which uses copy + shift instead of swap (used in bubble and selection sort))) However, a copy isn’t as time-consuming as a swap, so for random data this algo- rithm runs twice as fast as the bubble sort and faster than the selectionsort. Also author doesn't mention how time consuming shift is. From my POV copy is the simplest pointer assignment operation. While swap is 3x pointer assignment operations. Which doesn't take much time. Also shift of N elemtns is Nx pointer assignment operations. Please correct me if I'm wrong. Please explain, why what author says is true? I don't understand.

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• 10.10 - Error compiling kernel in iw_ndis.c

  - by chris

  I just wanted to compile a kernel (as described here), but I got this error: ubuntu/ndiswrapper/iw_ndis.c:1966: error: unknown field ‘num_private’ specified in initializer ubuntu/ndiswrapper/iw_ndis.c:1966: warning: initialization makes pointer from integer without a cast ubuntu/ndiswrapper/iw_ndis.c:1967: error: unknown field ‘num_private_args’ specified in initializer ubuntu/ndiswrapper/iw_ndis.c:1967: warning: excess elements in struct initializer ubuntu/ndiswrapper/iw_ndis.c:1967: warning: (near initialization for ‘ndis_handler_def’) ubuntu/ndiswrapper/iw_ndis.c:1970: error: unknown field ‘private’ specified in initializer ubuntu/ndiswrapper/iw_ndis.c:1970: warning: initialization makes integer from pointer without a cast ubuntu/ndiswrapper/iw_ndis.c:1970: error: initializer element is not computable at load time ubuntu/ndiswrapper/iw_ndis.c:1970: error: (near initialization for ‘ndis_handler_def.num_standard’) ubuntu/ndiswrapper/iw_ndis.c:1971: error: unknown field ‘private_args’ specified in initializer ubuntu/ndiswrapper/iw_ndis.c:1971: warning: initialization from incompatible pointer type Can anyone tell me what it means? Googling just came up with a result here on this site, where there was no answer, so maybe now someone knows.

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• Free libraries to work with Excel

  - by Danil Gholtsman

  I got some excel files, I need to read data from it and upload data to some database (I need to use firebird, but whatever). Right now I use <QAxObject> from Qt and code look like QAxObject* excel = new QAxObject("Excel.Application"); //pointer to excel //excel->setProperty("Visible", false); QAxObject* workbooks = excel->querySubObject("WorkBooks"); //get pointer to booklist workbooks->dynamicCall("Open (const QString&)", QString("C:\\databases\\test.xls")); //opening file, getting pointer to booklist QAxObject* workbook = excel->querySubObject("ActiveWorkBook"); QAxObject* worksheets = workbook->querySubObject("WorkSheets"); etc. The problem is that this way on users PC there must be installed Excel. Is there exists some free C++ libraries to work with *.xls, *.xlsx files without Excel installed?

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• monitoring unix resources from inside a process

  - by kamziro

  I've had a bunch of EAGAIN's from trying to fork() or spawning threads, which lead me to believe that I'm leaking resources somewhere. Is it possible, in POSIX, to get the following from inside the process itself: number of active pthreads number of active child processes number of active pipes number of active sockets (or maybe this and pipes would be counted as file descriptors?) Or do these have to be counted manually? There's already counters for them, but I think one of them are leaking.

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• MySQL query, 2 similar servers, 2 minute difference in execution times

  - by mr12086

  I had a similar question on stack overflow, but it seems to be more server/mysql setup related than coding. The queries below all execute instantly on our development server where as they can take upto 2 minutes 20 seconds. The query execution time seems to be affected by home ambiguous the LIKE string's are. If they closely match a country that has few matches it will take less time, and if you use something like 'ge' for germany - it will take longer to execute. But this doesn't always work out like that, at times its quite erratic. Sending data appears to be the culprit but why and what does that mean. Also memory on production looks to be quite low (free memory)? Production: Intel Quad Xeon E3-1220 3.1GHz 4GB DDR3 2x 1TB SATA in RAID1 Network speed 100Mb Ubuntu Development Intel Core i3-2100, 2C/4T, 3.10GHz 500 GB SATA - No RAID 4GB DDR3 UPDATE 2 : mysqltuner output: [prod] -------- General Statistics -------------------------------------------------- [--] Skipped version check for MySQLTuner script [OK] Currently running supported MySQL version 5.1.61-0ubuntu0.10.04.1 [OK] Operating on 64-bit architecture -------- Storage Engine Statistics ------------------------------------------- [--] Status: +Archive -BDB -Federated +InnoDB -ISAM -NDBCluster [--] Data in MyISAM tables: 103M (Tables: 180) [--] Data in InnoDB tables: 491M (Tables: 19) [!!] Total fragmented tables: 38 -------- Security Recommendations ------------------------------------------- [OK] All database users have passwords assigned -------- Performance Metrics ------------------------------------------------- [--] Up for: 77d 4h 6m 1s (53M q [7.968 qps], 14M conn, TX: 87B, RX: 12B) [--] Reads / Writes: 98% / 2% [--] Total buffers: 58.0M global + 2.7M per thread (151 max threads) [OK] Maximum possible memory usage: 463.8M (11% of installed RAM) [OK] Slow queries: 0% (12K/53M) [OK] Highest usage of available connections: 22% (34/151) [OK] Key buffer size / total MyISAM indexes: 16.0M/10.6M [OK] Key buffer hit rate: 98.7% (162M cached / 2M reads) [OK] Query cache efficiency: 20.7% (7M cached / 36M selects) [!!] Query cache prunes per day: 3934 [OK] Sorts requiring temporary tables: 1% (3K temp sorts / 230K sorts) [!!] Joins performed without indexes: 71068 [OK] Temporary tables created on disk: 24% (3M on disk / 13M total) [OK] Thread cache hit rate: 99% (690 created / 14M connections) [!!] Table cache hit rate: 0% (64 open / 85M opened) [OK] Open file limit used: 12% (128/1K) [OK] Table locks acquired immediately: 99% (16M immediate / 16M locks) [!!] InnoDB data size / buffer pool: 491.9M/8.0M -------- Recommendations ----------------------------------------------------- General recommendations: Run OPTIMIZE TABLE to defragment tables for better performance Enable the slow query log to troubleshoot bad queries Adjust your join queries to always utilize indexes Increase table_cache gradually to avoid file descriptor limits Variables to adjust: query_cache_size (> 16M) join_buffer_size (> 128.0K, or always use indexes with joins) table_cache (> 64) innodb_buffer_pool_size (>= 491M) [dev] -------- General Statistics -------------------------------------------------- [--] Skipped version check for MySQLTuner script [OK] Currently running supported MySQL version 5.1.62-0ubuntu0.11.10.1 [!!] Switch to 64-bit OS - MySQL cannot currently use all of your RAM -------- Storage Engine Statistics ------------------------------------------- [--] Status: +Archive -BDB -Federated +InnoDB -ISAM -NDBCluster [--] Data in MyISAM tables: 185M (Tables: 632) [--] Data in InnoDB tables: 967M (Tables: 38) [!!] Total fragmented tables: 73 -------- Security Recommendations ------------------------------------------- [OK] All database users have passwords assigned -------- Performance Metrics ------------------------------------------------- [--] Up for: 1d 2h 26m 9s (5K q [0.058 qps], 1K conn, TX: 4M, RX: 1M) [--] Reads / Writes: 99% / 1% [--] Total buffers: 58.0M global + 2.7M per thread (151 max threads) [OK] Maximum possible memory usage: 463.8M (11% of installed RAM) [OK] Slow queries: 0% (0/5K) [OK] Highest usage of available connections: 1% (2/151) [OK] Key buffer size / total MyISAM indexes: 16.0M/18.6M [OK] Key buffer hit rate: 99.9% (60K cached / 36 reads) [OK] Query cache efficiency: 44.5% (1K cached / 2K selects) [OK] Query cache prunes per day: 0 [OK] Sorts requiring temporary tables: 0% (0 temp sorts / 44 sorts) [OK] Temporary tables created on disk: 24% (162 on disk / 666 total) [OK] Thread cache hit rate: 99% (2 created / 1K connections) [!!] Table cache hit rate: 1% (64 open / 4K opened) [OK] Open file limit used: 8% (88/1K) [OK] Table locks acquired immediately: 100% (1K immediate / 1K locks) [!!] InnoDB data size / buffer pool: 967.7M/8.0M -------- Recommendations ----------------------------------------------------- General recommendations: Run OPTIMIZE TABLE to defragment tables for better performance Enable the slow query log to troubleshoot bad queries Increase table_cache gradually to avoid file descriptor limits Variables to adjust: table_cache (> 64) innodb_buffer_pool_size (>= 967M) UPDATE 1: When testing the queries listed here there is usually no more than one other query taking place, and usually none. Because production is actually handling apache requests that development gets very few of as it's only myself and 1 other who accesses it - could the 4GB of RAM be getting exhausted by using the single machine for both apache and mysql server? Production: sudo hdparm -tT /dev/sda /dev/sda: Timing cached reads: 24872 MB in 2.00 seconds = 12450.72 MB/sec Timing buffered disk reads: 368 MB in 3.00 seconds = 122.49 MB/sec sudo hdparm -tT /dev/sdb /dev/sdb: Timing cached reads: 24786 MB in 2.00 seconds = 12407.22 MB/sec Timing buffered disk reads: 350 MB in 3.00 seconds = 116.53 MB/sec Server version(mysql + ubuntu versions): 5.1.61-0ubuntu0.10.04.1 Development: sudo hdparm -tT /dev/sda /dev/sda: Timing cached reads: 10632 MB in 2.00 seconds = 5319.40 MB/sec Timing buffered disk reads: 400 MB in 3.01 seconds = 132.85 MB/sec Server version(mysql + ubuntu versions): 5.1.62-0ubuntu0.11.10.1 ORIGINAL DATA : This query is NOT the query in question but is related so ill post it. SELECT f.form_question_has_answer_id FROM form_question_has_answer f INNER JOIN project_company_has_user p ON f.form_question_has_answer_user_id = p.project_company_has_user_user_id INNER JOIN company c ON p.project_company_has_user_company_id = c.company_id INNER JOIN project p2 ON p.project_company_has_user_project_id = p2.project_id INNER JOIN user u ON p.project_company_has_user_user_id = u.user_id INNER JOIN form f2 ON p.project_company_has_user_project_id = f2.form_project_id WHERE (f2.form_template_name = 'custom' AND p.project_company_has_user_garbage_collection = 0 AND p.project_company_has_user_project_id = '29') AND (LCASE(c.company_country) LIKE '%ge%' OR LCASE(c.company_country) LIKE '%abcde%') AND f.form_question_has_answer_form_id = '174' And the explain plan for the above query is, run on both dev and production produce the same plan. +----+-------------+-------+--------+----------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+---------+----------------------------------------------------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+--------+----------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+---------+----------------------------------------------------+------+-------------+ | 1 | SIMPLE | p2 | const | PRIMARY | PRIMARY | 4 | const | 1 | Using index | | 1 | SIMPLE | f | ref | form_question_has_answer_form_id,form_question_has_answer_user_id | form_question_has_answer_form_id | 4 | const | 796 | Using where | | 1 | SIMPLE | u | eq_ref | PRIMARY | PRIMARY | 4 | new_klarents.f.form_question_has_answer_user_id | 1 | Using index | | 1 | SIMPLE | p | ref | project_company_has_user_unique_key,project_company_has_user_user_id,project_company_has_user_company_id,project_company_has_user_project_id | project_company_has_user_user_id | 4 | new_klarents.f.form_question_has_answer_user_id | 1 | Using where | | 1 | SIMPLE | f2 | ref | form_project_id | form_project_id | 4 | const | 15 | Using where | | 1 | SIMPLE | c | eq_ref | PRIMARY | PRIMARY | 4 | new_klarents.p.project_company_has_user_company_id | 1 | Using where | +----+-------------+-------+--------+----------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+---------+----------------------------------------------------+------+-------------+ This query takes 2 minutes ~20 seconds to execute. The query that is ACTUALLY being run on the server is this one: SELECT COUNT(*) AS num_results FROM (SELECT f.form_question_has_answer_id FROM form_question_has_answer f INNER JOIN project_company_has_user p ON f.form_question_has_answer_user_id = p.project_company_has_user_user_id INNER JOIN company c ON p.project_company_has_user_company_id = c.company_id INNER JOIN project p2 ON p.project_company_has_user_project_id = p2.project_id INNER JOIN user u ON p.project_company_has_user_user_id = u.user_id INNER JOIN form f2 ON p.project_company_has_user_project_id = f2.form_project_id WHERE (f2.form_template_name = 'custom' AND p.project_company_has_user_garbage_collection = 0 AND p.project_company_has_user_project_id = '29') AND (LCASE(c.company_country) LIKE '%ge%' OR LCASE(c.company_country) LIKE '%abcde%') AND f.form_question_has_answer_form_id = '174' GROUP BY f.form_question_has_answer_id;) dctrn_count_query; With explain plans (again same on dev and production): +----+-------------+-------+--------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+---------+----------------------------------------------------+------+------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+--------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+---------+----------------------------------------------------+------+------------------------------+ | 1 | PRIMARY | NULL | NULL | NULL | NULL | NULL | NULL | NULL | Select tables optimized away | | 2 | DERIVED | p2 | const | PRIMARY | PRIMARY | 4 | | 1 | Using index | | 2 | DERIVED | f | ref | form_question_has_answer_form_id,form_question_has_answer_user_id | form_question_has_answer_form_id | 4 | | 797 | Using where | | 2 | DERIVED | p | ref | project_company_has_user_unique_key,project_company_has_user_user_id,project_company_has_user_company_id,project_company_has_user_project_id,project_company_has_user_garbage_collection | project_company_has_user_user_id | 4 | new_klarents.f.form_question_has_answer_user_id | 1 | Using where | | 2 | DERIVED | f2 | ref | form_project_id | form_project_id | 4 | | 15 | Using where | | 2 | DERIVED | c | eq_ref | PRIMARY | PRIMARY | 4 | new_klarents.p.project_company_has_user_company_id | 1 | Using where | | 2 | DERIVED | u | eq_ref | PRIMARY | PRIMARY | 4 | new_klarents.p.project_company_has_user_user_id | 1 | Using where; Using index | +----+-------------+-------+--------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+---------+----------------------------------------------------+------+------------------------------+ On the production server the information I have is as follows. Upon execution: +-------------+ | num_results | +-------------+ | 3 | +-------------+ 1 row in set (2 min 14.28 sec) Show profile: +--------------------------------+------------+ | Status | Duration | +--------------------------------+------------+ | starting | 0.000016 | | checking query cache for query | 0.000057 | | Opening tables | 0.004388 | | System lock | 0.000003 | | Table lock | 0.000036 | | init | 0.000030 | | optimizing | 0.000016 | | statistics | 0.000111 | | preparing | 0.000022 | | executing | 0.000004 | | Sorting result | 0.000002 | | Sending data | 136.213836 | | end | 0.000007 | | query end | 0.000002 | | freeing items | 0.004273 | | storing result in query cache | 0.000010 | | logging slow query | 0.000001 | | logging slow query | 0.000002 | | cleaning up | 0.000002 | +--------------------------------+------------+ On development the results are as follows. +-------------+ | num_results | +-------------+ | 3 | +-------------+ 1 row in set (0.08 sec) Again the profile for this query: +--------------------------------+----------+ | Status | Duration | +--------------------------------+----------+ | starting | 0.000022 | | checking query cache for query | 0.000148 | | Opening tables | 0.000025 | | System lock | 0.000008 | | Table lock | 0.000101 | | optimizing | 0.000035 | | statistics | 0.001019 | | preparing | 0.000047 | | executing | 0.000008 | | Sorting result | 0.000005 | | Sending data | 0.086565 | | init | 0.000015 | | optimizing | 0.000006 | | executing | 0.000020 | | end | 0.000004 | | query end | 0.000004 | | freeing items | 0.000028 | | storing result in query cache | 0.000005 | | removing tmp table | 0.000008 | | closing tables | 0.000008 | | logging slow query | 0.000002 | | cleaning up | 0.000005 | +--------------------------------+----------+ If i remove user and/or project innerjoins the query is reduced to 30s. Last bit of information I have: Mysqlserver and Apache are on the same box, there is only one box for production. Production output from top: before & after. top - 15:43:25 up 78 days, 12:11, 4 users, load average: 1.42, 0.99, 0.78 Tasks: 162 total, 2 running, 160 sleeping, 0 stopped, 0 zombie Cpu(s): 0.1%us, 50.4%sy, 0.0%ni, 49.5%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 4037868k total, 3772580k used, 265288k free, 243704k buffers Swap: 3905528k total, 265384k used, 3640144k free, 1207944k cached top - 15:44:31 up 78 days, 12:13, 4 users, load average: 1.94, 1.23, 0.87 Tasks: 160 total, 2 running, 157 sleeping, 0 stopped, 1 zombie Cpu(s): 0.2%us, 50.6%sy, 0.0%ni, 49.3%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 4037868k total, 3834300k used, 203568k free, 243736k buffers Swap: 3905528k total, 265384k used, 3640144k free, 1207804k cached But this isn't a good representation of production's normal status so here is a grab of it from today outside of executing the queries. top - 11:04:58 up 79 days, 7:33, 4 users, load average: 0.39, 0.58, 0.76 Tasks: 156 total, 1 running, 155 sleeping, 0 stopped, 0 zombie Cpu(s): 3.3%us, 2.8%sy, 0.0%ni, 93.9%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 4037868k total, 3676136k used, 361732k free, 271480k buffers Swap: 3905528k total, 268736k used, 3636792k free, 1063432k cached Development: This one doesn't change during or after. top - 15:47:07 up 110 days, 22:11, 7 users, load average: 0.17, 0.07, 0.06 Tasks: 210 total, 2 running, 208 sleeping, 0 stopped, 0 zombie Cpu(s): 0.1%us, 0.2%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 4111972k total, 1821100k used, 2290872k free, 238860k buffers Swap: 4183036k total, 66472k used, 4116564k free, 921072k cached

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